1. Field of the Invention
The invention relates to a delivery system for water-insoluble, agriculturally active chemicals (AAC), and, more particularly, to an inert matrix composition (IMC) for forming both a microemulsion concentrate (MEC) and an aqueous microemulsion (AME) containing high loadings of such chemicals.
2. Description of the Prior Art
Agriculturally active chemicals are most preferably applied in the form of aqueous emulsions, solutions, or suspensions. Occasionally, they may also be applied in the form of a dust wherein the active ingredient is adsorbed onto or mixed with a finely divided inert carrier material, such as, china clay, or the like. With such powdered or dust compositions, drift due to wind is a problem and consequently, liquid formulations are preferred.
One of the problems with such liquid formulations is the fact that chemicals having agricultural activity often exhibit extreme insolubility in water. This results in their having to be dissolved either in organic solvents or utilized in the form of emulsions or suspensions. With respect to the use of organic solvents, these are generally disadvantageous from an environmental and cost viewpoint. Particularly, such organic chemicals may exhibit toxicity or side-effects which may be adverse to the effect of the agricultural chemical itself or to the subsequent fruit or vegetable produced in the particular agricultural use. This toxicity may also be disadvantageous with respect to handling.
When attempts are made to provide emulsified or suspension formulations, difficulties are encountered with respect to providing a desirably high concentration of the agriculturally active ingredient. Thus, when such agriculturally active chemicals are formulated into a macroemulsion (sometimes referred to herein as an emulsion), it is difficult to maintain the emulsified state. This, in turn, creates problems in maintaining a uniform formulation, particularly, when the formulation is diluted with water for application to the plants.
An attempt to provide concentrates of agriculturally useful chemicals for producing macroemulsions was disclosed in South African Patent Application No. 695,393, filed Jul. 25, 1969. This application was directed to the formulation of a concentrate substantially water-insoluble pesticides for agricultural use. The pesticides, either in oil or solid form, were mixed with pyrrolidones having a hydrogen or a lower alkyl group containing from 1 to 4 carbon atoms attached to the nitrogen atom of the pyrrolidone ring. The application disclosed that concentrated solutions of difficult to dissolve pesticides could be formulated and that such concentrates exhibited good stability. The concentrates utilized were those containing the pesticidal active ingredient, the particular lower alkyl pyrrolidone, a co-solvent which is usually a common organic solvent, such as, an aromatic including xylene, methylated and polyalkylated naphthalenes and aliphatic solvents, and a dispersing or emulsifying agent, such as, a surfactant, including polyoxyethylene alkylphenols, polyoxyethylene fatty esters, polyoxyethylene sorbitan fatty esters which may be blended with oil-soluble sulfonates, calcium and aminosulfonate salts, and the like.
However, this prior art did not offer a solution to the problem arising from the difficulty in maintaining the stability of the emulsion formed after the concentrate was diluted with water. Consequently, unless the diluted form of the concentrate was used immediately after emulsification, it was difficult to provide a stable diluted formulation for application to the plants, soil, pests, and the like.
In addition, for such agricultural uses, it is also desirable to avoid the use of toxic solvents, including those of Lists 1 and 2 of 40 C.F.R. 154.7 dated Apr. 22, 1987, which includes inerts of toxicological concern and solvents having high flash points, as well as to increase the amount of the agriculturally active material in the concentrate. Moreover, many organic solvents which have been used in the past, even those exhibiting relatively low toxicities, are not biodegradable and thus remain as a pollutant.
The Parent Applications referred to hereinabove have provided solutions to the problem of providing stable macroemulsions of insoluble agricultural chemicals in aqueous systems. This was accomplished by the use of long and short chain alkyl lactams for formation of emulsifiable concentrates of agricultural chemicals. See also U.S. Pat. No. 5,093,031, the contents of which are incorporated herein by reference, which disclosed the use of long chain alkyl lactams to prepare emulsifiable concentrates of water-insoluble, agriculturally active ingredients, e.g., herbicides, fungicides, pesticides, and the like, which on dilution with water, formed stable macroemulsions.
More particularly, Narayanan, in U.S. Pat. No. 5,071,463, described an emulsifiable concentrate comprising a macroemulsion of an agriculturally active chemical, N-methyl pyrrolidone, N-octyl pyrrolidone and an anionic surfactant such as Gafac RE-610 (an ethoxylated phosphate ester). Only a small amount of anionic surfactant was required to form a macroemulsion with up to 40% by weight of the active chemical. However, the macroemulsion was cloudy and it was necessary to use the aqueous macroemulsion soon after preparation.
Accordingly, it is an object of this invention to provide an aqueous microemulsion in which relatively high loadings of the water-insoluble, agriculturally active chemical can be accommodated in the micelles of the microemulsion, which are clear, stable and efficacious, and, particularly, in which both the microemulsion concentrate (before dilution with water) and the aqueous microemulsion (after dilution with water) can be stored indefinitely at or below room temperature before use.
Another object herein is to provide an inert matrix composition from which the microemulsion concentrate and the aqueous microemulsion can be prepared conveniently.
A particular object of this invention is to provide an aqueous microemulsion of a water-insoluble, agriculturally active chemical at a high chemical loading which is solvated and stable within a close packed micelle of predetermined dimensions.